This research project aims to define the organization of the adenovirus genome in terms of the location and function of the viral genes controlling virus development in the lytic infection, and to define the requirements for adeno gene products in the initiation and maintenance of oncogenic transformation in rodent cells. Temperature-sensitive (ts) and host-range (hr) mutants of type 5 adenovirus comprising 19 complementation groups have been isolated, and are being characterized genetically and physiologically. Mutations representative of each complementation group have been mapped physically by marker rescue using an improved transfection technique for adeno DNA and DNA-protein complex. The hr mutants fall into two complementation groups, each of which is defective for transformation; mutations representative of group I map in early region 1a, and those of group II map in the contiguous region 1b. The improved marker rescue method is being used to introduce specific DNA fragments mutated in vitro into the viral genome, and in this way we have recently isolated cold-sensitive (cs) hr mutants belonging to complementation groups I and II. These mutants are cs for transformation, and preliminary evidence indicates that some of the mutations alter a gene product required for maintenance of transformation. Phenotypic characterization of these cs mutants, and cells transformed by them, is currently in progress.